1. Field of the Invention
This invention relates to a hub and axle assembly for a bicycle, more particularly to a hub and axle assembly which includes a bowl bearing mounted between the axle and a hub shell and which is adapted to be coupled to a uni-directional driving sprocket mechanism of the bicycle.
2. Description of the Related Art
Referring to FIG. 1, a conventional bicycle front hub 100 is shown to include a hub shell 1 with two ends, and an axle 2 extending through the two ends of the hub shell 1. Each end of the hub shell 1 is formed with an inner recess 101 so as to receive a bowl-shaped surrounding race member 301. The surrounding race member 301 has a bearing race surface for receiving a rolling member 302. A mounting sleeve member 303 is sleeved on the axle 2 and has a surrounding race portion 304 facing toward the surrounding race member 301 to cooperate with the surrounding race member 301 and the rolling member 302 to form an anti-friction bearing. A screw nut 4 is disposed to secure the mounting sleeve member 303 on the axle 2.
Since the surrounding race member 301 is generally made to have an outer diameter of 29.5 mm, the inner recess 101 in the hub shell 1 is required to have an inner diameter larger than 29.5 mm. Moreover, since a sprocket wheel mechanism of the bicycle is generally made to have an internal diameter of 30 mm, the hub shell 1 is required to have a threaded engaging portion with an outer diameter of 30 mm when the bicycle hub 100 is assembled on a rear part of the bicycle. However, it is difficult to make such a threaded engaging portion on the hub shell 1.
Referring to FIG. 2, another conventional bicycle hub 200 is shown to include a hub shell 5, and an axle 7 extending through two ends of the hub shell 5. One end of the hub shell 5 is formed with a threaded engaging portion 501 with an outer diameter of 30 mm for threadedly engaging a sprocket wheel mechanism (not shown) of the bicycle. A ball bearing unit 6, such as type 6804 of SKF which has an inner diameter of 15 mm and an outer diameter of 24 mm, is interposed between the hub shell 5 and the axle 7. However, this type of the bearing unit 6 is expensive and results in a relatively high manufacturing cost for the bicycle hub 200.
The object of the present invention is to provide a hub and axle assembly which is adapted to be coupled to a uni-directional driving sprocket wheel mechanism of a bicycle and which is economical to manufacture.
According to this invention, the hub and axle assembly includes an axle extending along an axis, and a hub shell which is rotatably mounted on the axle. The hub shell has left and right lateral ends disposed opposite to each other in an axial direction, and an inner peripheral wall extending in the axial direction to communicate the left and right lateral ends and spacedly surrounding the axle. The inner peripheral wall includes left and right wall segments disposed respectively proximate to the left and right lateral ends, and an intermediate wall segment interposed therebetween and defining a diameter smaller than that of the left wall segment so as to form a left surrounding shoulder that faces toward the left lateral end. A mounting sleeve member is sleeved on the axle, and has a surrounding race portion disposed proximate to and spaced apart from the left surrounding shoulder along an inclined line which forms an acute angle with the axis, and a surrounding abutment portion opposite to the surrounding race portion and proximate to the left lateral end. A surrounding race member has an attachment wall surface abutting against the left surrounding shoulder, and a race wall surface disposed opposite to the attachment wall surface along the inclined line and spaced apart from the surrounding race portion along the inclined line. A rolling member is interposed between and cooperates with the surrounding race portion and the race wall surface of the surrounding race member to serve as an anti-friction bearing between the mounting sleeve member and the left surrounding shoulder. The rolling member has a diameter co-linear with the inclined line. A tubular mount member includes a tubular engaging portion for engaging the left wall segment while being spaced apart from the surrounding abutment portion in radial directions, and a tubular mount portion which extends from the tubular engaging portion in the axial direction and outwardly of the left lateral end and which is adapted to be driven by a uni-directional driving sprocket wheel mechanism. A retaining member is secured to the axle to prevent the surrounding abutment portion from moving away from the rolling member.